A new tick-borne virus, Heartland virus (HLV), associated with severe febrile illness has recently been reported in the US. HLV is closely related to the severe fever with thrombocytopenia syndrome virus (SFTSV), a tick transmitted virus, with a case fatality rate as high as 30%, putting it on par with yellow fever, Lassa fever, hantavirus pulmonary syndrome, Crimean-Congo hemorrhagic fever, and untreated Rocky Mountain spotted fever. As HLV is a newly described virus in the US, its the incidence of infection, range of disease severity and pathogenesis are currently unknown. So far, 6 human cases have been reported with one fatal case. Lack of an animal model is a critical barrier to understand the pathogenesis and host immune response to HLV infection, and also impedes development of tools for prevention and control of HLV infection. The proposed study is innovative in that it is the first to develop an animal model for HLV infection by infected tick bites, and also in its rapid response to a newly identified human pathogen. This study will have an impact on US public health, and will further advance our current understanding of HLV infection and probably SFTSV infection as well.